What is the point of RewriteRule ^index\.php$ – [L] in htaccess?

Hello, I am trying to figure out what this line does in my htaccess file and why it is necessary:

RewriteRule ^index\.php$ – [L]

I have read in numerous places that this is there because we need ignore a request to index.php. But what I don’t get is, why? Won’t it don’t rewrite something to itself anyways?

Thanks.